The Twin Falls gate pivots straight up in a most grand manner
 

Unfortunately it has no safety switches

                             
 History of the Gate

This  "Sun Power" gate was purchased and installed in 1993 by the new owners of the 180 acres surrounding King Lake.

The gate fell into disrepair after a few years. It quit working and was left open for several more years.

In 1999 vandals started a forest fire at the end of the road and the owners had to fix the gate to limit people on the roads.

Some residents living up the road got together and hired a local electronics tech to take over the maintenance, upkeep and maintain the keypad access list.

The "free exit" loop eventually failed and was replaced  with an aftermarket loop sensor.

The new loop sensor was connected and a puzzling situation developed.

 The Problem

If the gate was open for car A to enter, and Car B drove past the free exit sensor, the gate would abruptly and rapidly close without warning.

This situation happened more times than you would think.

The gate would also close quickly if one car tried to 'tailgate' another car through the gate and wasn't fast enough.

The first car would trigger an immediate close on top of the second car.

Similarly, large trucks could trigger the close sensor before they were completely through the gate.

The community put out a letter that warned people to watch for situations where two cars met at the gate and triggered the exit loop.

The gate never had any schematics for the logic box and commercial gate companies just scratched their heads.

There was no way to figure out the gate logic so we came up with an idea to disable the exit loop sensor when the gate was open. This would allow any cars to arrive and depart as long as the 2 minute "open" timer was counting down.

This scheme involved repurposing a sensor used to count objects off of a conveyor belt. We'd use it to "optically" sense the gate position and open the circuit to the exit loop as long as the gate was open

 

Here's the opening mechanism or "operator"
The seven big springs in the box effectively counterbalance the weight of the gate so that a small battery-powered motor can open and close the gate.
 

This big "foot" is connected to the gate and is pulled on by the springs.
Yellow thing is the conveyor belt sensor we used to sense the gate position.
Its called an OPBT2 by Banner Industries

Final Testing on the bench
 

Control Box mounting

The new control box

             
                                  Design Criteria

The device should not be physically wired to the gate logic except to interrupt the incoming signal from the exit detector.

The device had to be simple, foolproof and easy to install.

The parts count should be the minimum necessary.

The device could never cause the gate to close.

The device has to be wired into the gate box a non invasive way.

The device has to run on 12 volt power.

The device should have a "bypass" switch in case of a failure of the parts in the control box

The device should have sufficient indicator lights so anyone looking at the front panel will know what it is doing.

The device should have a fuse or circuit breaker.

The device should incorporate a counter so the maintainers have an idea of how many the times the gate has opened and closed.
 

Logic circuit
 

Schematic diagram

An early drawing of the proposed system

Fire truck and crew  in 2019
Trying to figure out how the gate operates and how to open it!

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10/21/21